Ironworker punching guidelines tonnage requiements for punching round and shaped holes. This chart is used for mild steel and other metal material types. Standard shape holes are oblong, square and hexagonals. Metal fabricators will need to check the tonnage on the ironworker model to be used to make the machine are enough tonnage. The general rule of thumb is to not punch a hole that is smaller than the material thickness. Thank you to Cleveland Steel Punch for the different guidelines